CA1333760C - High index photochromic glasses - Google Patents
High index photochromic glassesInfo
- Publication number
- CA1333760C CA1333760C CA000593311A CA593311A CA1333760C CA 1333760 C CA1333760 C CA 1333760C CA 000593311 A CA000593311 A CA 000593311A CA 593311 A CA593311 A CA 593311A CA 1333760 C CA1333760 C CA 1333760C
- Authority
- CA
- Canada
- Prior art keywords
- li2o
- photochromic
- zro2
- glass
- tio2
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C4/00—Compositions for glass with special properties
- C03C4/04—Compositions for glass with special properties for photosensitive glass
- C03C4/06—Compositions for glass with special properties for photosensitive glass for phototropic or photochromic glass
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/062—Glass compositions containing silica with less than 40% silica by weight
- C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/062—Glass compositions containing silica with less than 40% silica by weight
- C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
- C03C3/066—Glass compositions containing silica with less than 40% silica by weight containing boron containing zinc
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/062—Glass compositions containing silica with less than 40% silica by weight
- C03C3/064—Glass compositions containing silica with less than 40% silica by weight containing boron
- C03C3/068—Glass compositions containing silica with less than 40% silica by weight containing boron containing rare earths
-
- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C3/00—Glass compositions
- C03C3/04—Glass compositions containing silica
- C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
- C03C3/11—Glass compositions containing silica with 40% to 90% silica, by weight containing halogen or nitrogen
Landscapes
- Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Geochemistry & Mineralogy (AREA)
- Materials Engineering (AREA)
- Organic Chemistry (AREA)
- Glass Compositions (AREA)
Abstract
The present invention is related to transparent, fast darkening and fading photochromic glasses.
The glasses contain SiO2, B2O3, Al2O3, ZrO2, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, La2O3, Nb2O5, TiO2 as base glass components, Ag, Br, Cl, CuO as photochromic elements, with, optionally, Sb2O3, As2O3, and SnO2 as colorants to impart a brown color at darkening.
The glasses have a refractive index greater than 1.585, an Abbe number greater than 42, and a density lower than about 2.80 g/cm3.
The glasses contain SiO2, B2O3, Al2O3, ZrO2, Li2O, Na2O, K2O, MgO, CaO, SrO, BaO, ZnO, La2O3, Nb2O5, TiO2 as base glass components, Ag, Br, Cl, CuO as photochromic elements, with, optionally, Sb2O3, As2O3, and SnO2 as colorants to impart a brown color at darkening.
The glasses have a refractive index greater than 1.585, an Abbe number greater than 42, and a density lower than about 2.80 g/cm3.
Description
-HIGH INDEX PHOTOCHROMIC GLASSES
Background of the Invention The present invention is related to high index, low dispersion, low density and fast darkening and fading photochromic glasses for ophthalmic lenses.
In the present context, fast darkening and fading glasses means glasses which show at room temperatures after 15 minutes' exposure to an actinic illumination, a luminous transmission lower or equal to 40% and a luminous transmis-sion greater than about 55% five minutes after they havebeen removed from the actinic source.
Most of prior art patents dealing with photochromic glasses describe compositions to obtain products, for ophthalmic applications or not, having a refractive index equal to about 1.523.
Ophthalmic lenses of high refractive index present numerous advantages. In fact, using a high index glass instead of a standard glass (nD=1.523) allows, for a given power, a thickness reduction of the edge (negative power) or of the center (positive power).
Increasing the index of refraction leads generally to a decrease of the Abbe number (or an increase of glass dispersion). In order to minimize the defects induced by the increase of the glass dispersion, mainly colored fringes at the edge of the lens, the glass must have a high Abbe number.
/ ~
133376~
Associated with thickness reduction, another signifi-cant advantage can be a lower weight. For that the glass must display a low density; a density less than or equal to 2.80 g/cm3 is necessary.
The objective of this invention is to combine these advantages of a high refractive index glass, including the above-mentioned criteria, with the advantages of a photo-chromic glass. This has become a necessity because within a few years the use of glasses with a 1.6 index of refrac-tion will tend to replace for ophthalmic applications the current glasses having a refractive index of 1.523. Thus, the wearer of corrective eye-glasses would get simultane-ously the comfort given by a high index lens and the functionality of a photochromic glass.
Summary of the Invention The object of the present invention is to provide a photochromic lens of high index of refraction with rapid darkening and fading. A suitable photochromic glass is provided having a refractive index greater than 1.585, an Abbe number greater than 42, a density lower than 2.80 g/cm3, a liquidus viscosity of a least 200 poises, and, for a 2 mm thickness, exhibits the following optical properties:
(1) a luminous transmission in the unexposed state (To) greater or equal to about 84%;
(2) a luminous transmission, in the darkened state after 15 minutes' exposure to an actinic radiation (TD15) at a temperature in the 0 to 25C range, less than about 40% and preferably less than 35%;
Background of the Invention The present invention is related to high index, low dispersion, low density and fast darkening and fading photochromic glasses for ophthalmic lenses.
In the present context, fast darkening and fading glasses means glasses which show at room temperatures after 15 minutes' exposure to an actinic illumination, a luminous transmission lower or equal to 40% and a luminous transmis-sion greater than about 55% five minutes after they havebeen removed from the actinic source.
Most of prior art patents dealing with photochromic glasses describe compositions to obtain products, for ophthalmic applications or not, having a refractive index equal to about 1.523.
Ophthalmic lenses of high refractive index present numerous advantages. In fact, using a high index glass instead of a standard glass (nD=1.523) allows, for a given power, a thickness reduction of the edge (negative power) or of the center (positive power).
Increasing the index of refraction leads generally to a decrease of the Abbe number (or an increase of glass dispersion). In order to minimize the defects induced by the increase of the glass dispersion, mainly colored fringes at the edge of the lens, the glass must have a high Abbe number.
/ ~
133376~
Associated with thickness reduction, another signifi-cant advantage can be a lower weight. For that the glass must display a low density; a density less than or equal to 2.80 g/cm3 is necessary.
The objective of this invention is to combine these advantages of a high refractive index glass, including the above-mentioned criteria, with the advantages of a photo-chromic glass. This has become a necessity because within a few years the use of glasses with a 1.6 index of refrac-tion will tend to replace for ophthalmic applications the current glasses having a refractive index of 1.523. Thus, the wearer of corrective eye-glasses would get simultane-ously the comfort given by a high index lens and the functionality of a photochromic glass.
Summary of the Invention The object of the present invention is to provide a photochromic lens of high index of refraction with rapid darkening and fading. A suitable photochromic glass is provided having a refractive index greater than 1.585, an Abbe number greater than 42, a density lower than 2.80 g/cm3, a liquidus viscosity of a least 200 poises, and, for a 2 mm thickness, exhibits the following optical properties:
(1) a luminous transmission in the unexposed state (To) greater or equal to about 84%;
(2) a luminous transmission, in the darkened state after 15 minutes' exposure to an actinic radiation (TD15) at a temperature in the 0 to 25C range, less than about 40% and preferably less than 35%;
(3) a fading rate at ambient temperature (20 to 25C) such that, five minutes after it has been removed from the actinic light, the glass has a luminous transmission (TF5) of at least 55% and preferably, in excess of 60%;
(4) a difference between the luminous transmissions of the darkened state over the temperature range of 25C to ~ ~, _ ~3~ 1333760 40C less than 23 points of transmission and preferably less than or equal to 20 points.
This last parameter reflects the temperature dependence of the glasses according to the invention and in relation with parameters (1), (2), and (3), describes the optical characteristics of the lens over the extent of the 20 to 40C temperature range. Furthermore, the color character-istics of the lens in the clear state as well as in the darkened state are described by the trichromatic coordinates which will be explained hereinafter.
The above optical and photochromic properties of the present glasses are obtained in the alkali, aluminoboro-silicate composition family which contain niobium oxide.
In contrast to the photochromic glasses with an index of refraction of 1.523, the compositions described in this invention must necessarily contain oxides which contribute strongly to the index of refraction such as La2O3, Nb2O5, TiO2, CaO, SrO, and BaO in appreciable quantities when they are present in the composition in order to satisfy the above-mentioned criteria.
The base glass compositions consist essentially, expressed in terms of weight percent on the oxide basis, of:
SiO233-50 MgO 0-5 B2O315-25 CaO 0-5 SiO2+B2O358-66 SrO 0-10 Al2O3 2-9 BaO 0-10 Zr2 1-5 ZnO 0-5 Al2O3+ZrO2 4-10 MgO+CaO+SrO+BaO+ZnO 1-15 (XO) Li2O1.5-6 X2O+XO 10-24 Na2O0-4 La23 0-5 Li2O+Na2O+K2O 7-16 (X2O) TiO2 2 8 Li2o/x2o 0.20-0.50 Zro2+Tio2+Nb2os+La2o3 14-23 The preferred base glasses consist essentially of:
~4~ 1 3 3 3 7 ~ 0 SiO2 36-48 . MgO 0 B2O3 15-20 CaO 0 SiO2+B2O3 57-63 SrO 2-8 Al2O3 5-8 BaO 0 Zr2 1-4 ZnO 0 Al2O3+ZrO2 6-10 MgO+CaO+SrO+BaO+ZnO 2-9 (XO) Li2O 2-5.5 X2O+XO 10-20 Na2O 0.3-2.5 La23 K2O 3-8 Nb25 8 14 Li2O+Na2O+K2O 8-12 (X2O) TiO2 2 7 i O/X O 0 35-0.50 ZrO2+TiO2+Nb2O5 2 3 In addition to the composition of the base glass, the obtaining of photochromic properties such as are defined above requires the introduction of photochromic elements in the following proportions, expressed in terms of weight percent as analyzed in the glass:
Ag 0.130-0.280 Br 0.130-0.220 Ag+Br >0.270 Cl 0.170-0.360 CuO 0.0070-0.0350 The preferred proportions consisting essentially of:
Ag 0.135-0.180 8r 0.140-0.170 Ag+Br >0.280 Cl 0.200-0.300 CuO 0.0120-0.0300 Chlorine is used in quantities of 0.17-0.36%, prefera-bly 0.2-0.3%, as analyzed in weight percent in the glass.
It is an indispensable element which, when present in the correct proportions, permits the desired photochromic performance to be obtained. Its inclusion at too low a level leads to glasses exhibiting insufficient darkening, ~5~ 1333760 `_ whereas too high a content decreases the fading rate and the sensitivity of the glass to visible light.
The CuO content is 0.0070-0.0350, preferably 0.0120-0.0300, as analyzed in weight percent in the glass. CuO
acts as a "sensitizer" of silver halides and, therefore, its level in the glass must be carefully controlled. Below 0.0070%, the darkening of the glass is insufficient. On the other hand, above 0.030%, the temperature dependence of the glass becomes unacceptable.
The limits of the above-specified ranges for the constituents of the base glass are equally crucial in order to obtain glasses exhibiting good melting and forming capability, and possessing the chemical and physical properties, e.g., strengthening by chemical and/or physical tempering and good durability, demanded of glasses to be utilized in optical and ophthalmic applications, as well as the required photochromic behavior. More specifically, the viscosity at the liquidus temperature must be sufficient to permit pressing employing conventional forming techniques, i.e., a liquidus viscosity equal to or greater than about 200 poises.
SiO2 and B2O3 constitute the basic components of this type of glass. Their sum determines the quantity of other oxides and influences the devitrification characteristics.
It will be greater than 58% and lower than 66%. This condition is not sufficient to get the requested photo-chromic performances. The aptitude to precipitate silver halides, in an appropriate temperature range, depends on the amount of B2O3. It must not be lower than 15%. It is also known that B2O3 imparts a negative effect on the glass chemical durability and therefore the maximal content is fixed at 25% and preferably 20%.
Al2O3 is important because it affects the ability to retain in the glass Ag, Br, and Cl. For that reason, 2% at least, will be present and preferably at least 5%. In addition, Al2O3 stabilizes the glass against the natural -6- 13337~
tendency of these glasses to phase separation and as ZrO2, Al2O3 improves the chemical durability of the glass.
Furthermore, A12O3 increases considerably the glass viscosity which is favorable for the viscosity at the liquidus.
Zr2 improves the durability against alkaline attack and 1% at least must be present. It contributes signifi-cantly to the refractive index but also, increases quickly the crystallization characteristics of the glass. There-fore, a maximum of 5% will be present in the glass. It hasbeen observed that in high alumina glasses, the ZrO2 amount must be limited to avoid devitrification. Thus, the sum (Al2O3 + ZrO2) should be between 4 and 10%, and preferably between 6 and 10%.
Along with their small contribution to the density of the glass, the alkalies (Li2O, Na2O, K2O) are necessary to obtain the desired photochromism.
Among the alkalies, Li2O makes it possible to obtain the desired fading rate. The glass will contain at least 1.5% Li2O and preferably at least 2%. However, it decreases considerably the viscosity and increases the tendency to devitrification and phase separation. The maximum content is 6%, and preferably 5.5%.
Na2O is favorable to increase the mechanical strength which can be obtained by chemical strengthening. Conse-quently, the glasses will contain preferably at least 0.3%
Na2O. Due to its negative effect on the fading rate, a maximum of 4% will be used.
K2O is used in conjunction with Li2O at 2 to 9 wt. %
and preferably at 3 to 8 wt. %. In fact, as already mentioned, Li2O makes it possible to obtain fast fading glasses. However, inasmuch as the photochromic behavior is the result of two opposite mechanisms occurring simultane-ously (darkening and thermal fading), a too high fading rate will lead generally to a low darkening glass. K2O
enables one to get dark glasses without affecting too much the fading rate when present at 2 to 9%.
In a general way, the combination of the three alkali oxides is preferred. In this case, as mentioned previously, the following conditions should be satisfied:
7 < X O < 16 0.20 < Li2O/X2O < 0.6 with X2O = Li2O + Na2O + K2O.
The main contributor to the refractive index is Nb2O5.
Its effect on index is close to TiO2 but it is not as powerful as TiO2 to increase the glass dispersion. Further-more, it is equivalent to Al2O3 for the photochromic performances.
Nb2O5 must be present at a level of at least 8%.
However, being very expensive, a maximum of 16% and prefer-ably of 14% will be used.
TiO2 has no specific effect on the photochromic properties. At least 2% will be introduced in the glass.
High TiO2 content would impart to the glass an undesirable yellow coloration and would enhance the tendency to phase separation. For those reasons, the TiO2 content will not exceed 8% and preferably will be lower or equal to 7%.
In order to increase the refractive index, oxides such as: MgO, CaO, SrO, BaO, ZnO, and Li2O3 can also be added to the base glass. Among the divalent oxides, MgO and CaO
have a small contribution to the density but also to the refractive index. However, although the desired photo-chromic performances can be obtained with those oxides, SrO
will be preferred according to the invention. SrO
stabilizes the glass toward devitrification and phase separation. Consequently, SrO will be present in the glass at a level equal to or greater than 2% and lower than 8%.
To satisfy the constraints on refractive index and on density, the sum of divalent oxides (MgO + CaO + SrO + BaO
+ ZnO = XO) must meet the following condition:
1 < XO < 15 preferably 2 < XO < 12 and most particularly 2 < XO < 9.
1~33760 Furthermore, in presence of alkalies (Li2O, Na2O, K2O) and to have a glass stable against devitrification, the sum (X2O+XO) must fulfill the condition: 10 < X2O + XO < 24.
Finally, La2O3 not only strongly increases the refrac-tive index but also the density. The glass will notcontain more than 5% and preferably it will be absent from its composition.
With the limitations above mentioned and taking into account the required characteristics, the oxides having a large contribution to the refractive index such as ZrO2, TiO2, Nb2O5, and La2O3 must satisfy in a general way the condition:
r2 + TiO2 + Nb2Os + La23 < 23 The compositions which meet the conditions above mentioned, lead to glasses displaying all the optical and photochromic characteristics described in this invention.
The natural color of the glasses is, in the clear or unexposed state, slightly yellow or green and, in the darkened state, gray or brown-gray.
The glasses according to the invention can also be brown in the darkened state. Generally, and as described in prior art patents, to obtain a brown tint at darkening, noble metals such as Pd and Au, are added.
The brown photochromic glasses according to the invention, contain elements such as Sb2O3, AS2O3, and/or SnO2 .
For a given composition and to get a significant coloration, the sum of these oxides must be equal, at least, to 0.10%. However, it will be lower than 1% because they are also powerful redox agents. The values given are in weight percentage as analyzed in the glass.
According to a preferred embodiment of the invention, antimony oxide will be used to get a brown glass at darken-ing. The maximal Sb2O3 content is 0.65%. Above that value, Sb2O3 imparts to the glass a too strong yellow coloration in the clear state, i.e., the transmission To would be too low. In order to avoid undesirable effects _ -9- 1333760 (too reduced glass, Ag metallic precipitation), Sb2O3 will be used with preferred compositions for Ag, Cl, Br, CuO as defined previously.
Those "colorants" give to the glass in the clear _ state, a slightly yellow tint. If necessary, it can be attenuated by addition of colorant oxides such as Er2O3, CoO, ~r Nd2O3.
Prior Art U. S. Patent No. 3,630,765 discloses photochromic glasses exhibiting refractive indices higher than 1.54.
The essence of the inventive glasses comprised adding 10-50% by weight Ta2O5 to silver halide-containing, alkali metal aluminoborosilicate base glass compositions to raise the refractive index thereof. No mention is made of Nb2O5, TiO2, and/or ZrO2.
U. S. Patent No. 3,703,388 is expressly directed to high refractive index photochromic glasses. The glasses -20 consisted essentially, in weight percent, of 15-75% La203, 13-65% B2O3, the sum La2O3 + B2O3 being at least 30%, with silver halides being present there. Various proportions of Nb2O5, TiO2, and ZrO2 are mentioned as optional components.
Nevertheless, the base glass compositions are far afield from those of the present invention.
U. S. Patent No. 3,999,996 is drawn to silver halide-containing photochromic glasses demonstrating refractive indices >1.60 having base glass compositions consisting essentially, in weight percent, of:
SiO2 10-20 ZrO2 0.5-3 B2O3 15-23 TiO2 0.2-3 PbO 26-30 K2O 0.1-2 ZnO 3-5 Na2O 0.1-2 La2O3 6-10 Li2O 0.1-4 Such compositions are very remote from those of the present invention .
-lO- 1333760 U. S. Patent No. 4,149,896 is concerned with silver halide-containing photochromic glasses exhibiting refractive indices in excess of 1.60 having base compositions consist-ing essentially, in weight percent, of:
SiO2 5 30 Zr2 0-6 B2O3 7-35 i 2 3 PbO 6-26 K2O 0-2 ZnO 0-15 Na2O 0-2 La23 12-30 Li2O 0-4 A12O3 12-25 Bi2O3 and/or Ta2O5 and/or Nb2O3 and/or WO3 0-5 Such compositions are quite removed from the ranges of the present invention.
U. S. Patent No. 4,486,541 describes silver halide-containing photochromic glasses exhibiting refractive indices 21.59 claiming base compositions consisting essen-tially, in weight percent, of:
SiO232-47 wo3 0-1 B2O314.5-27 MgO 0-1 P2O50-11 CaO 0-6 SiO2+B2O3+p2o558-71 SrO 0-24 A1230-0.4 PbO 0.5-12 Zr21.5-10 TiO2 0.5-8 La2O30-23 Li2O 0.5-6 Nb25 0-2 Na2O 0-4 Ta2O50-18 R2O 6-12 wherein Li2O+Na2O+R2O 6.5-15 and l2o3+zro2+La2O3+Nb2Os+Ta2O5~WO3 2-25 and wherein MgO+CaO+SrO 2-24 and wherein La2O3 SrO PbO TiO2 Nb2O5 ZrO2 WO3 Ta2O5 12 34 Such compositions are outside of those of the present invention at least with respect to A12O3, Nb2O5, and PbO.
U. S. Patent No. 4,686,196 presents silver halide-containing photochromic glasses demonstrating refractive indices 21.59 claiming base compositions consisting essen-tially, in weight percent, of:
SiO2 42-56 SrO 0-3 B2O3 11-18 BaO 0-6 Al2O3 0-5 ZnO 0-2 2+B2O3+Al2O3 55-75 MgO+CaO+SrO+BaO+ZnO 3-12 Li2O 3-9 TiO2 3.06-6.74 Na2O 0-7.98 Zr2 2-11 K2O 0-8.22 Nb2O5 2.28-8 Li2O+Na2O+K2O 7-15 La23 0-3 MgO 3-12 PbO 0-2 CaO 0-3 r23 0-1 Such compositions are low in Nb2O5 and SrO and require the presence of MgO.
Description of Preferred Em~odiments The following examples, which must be deemed illustra-tive only and not limitative, describe the invention.
Compositions are given in Table I. The quantities of components are expressed in parts-by weight on the oxide basis. Taking into account that the total of components is equal to or close to 100, the given values can be considered as weight percent.
As the cation(s) to which halogens are bound are not known, and because they are present in small amounts, they are reported as chlorine and bromine in agreement with the usual practice. Silver, present also in small amounts, is given as the metal.
The reported values for Ag, Cl, Br, CuO, Sb203, and SnO2 are, in general, as analyzed in the glasses, except if specifically mentioned otherwise.
Batches are prepared from raw materials, oxides, or ' other compounds which, when they are melted together, are converted into the desired oxides at the required level.
Chlorine and bromine are generally incorporated as halides of alkali metals. Components used to tint the glass are generally added as oxides or compounds of the metal.
Ingredients of the raw materials batch are weighed and carefully mixed (ballmilled) to help in achieving homogene-ity of the melted glass. Then they are charged into a _ platinum crucible, that crucible is introduced into a furnace heated by Joule effect, and the batch is melted at 1350C for about 3 hours. After casting to form a slab, the glass is annealed at about 450C.
Table I
SiO2 39.64 40.42 39.82 38.48 B2O3 21.20 21.62 21.30 20.58 Al23 6.21 6.33 6.24 6.03 ZrO2 2.50 2.55 2.51 2.43 Li2O 4.40 4.48 4.42 4.27 Na2O 1.26 1.28 1.26 1.22 K2O 5.26 5.36 5.28 5.10 CaO - 2.32 Nb25 10.79 11.00 10.84 10.47 TiO2 2.43 2.48 2.44 2.36 SrO 6.31 2.14 4.23 BaO - - - 9.06 ZnO - - 1.66 SiO2+B2O3 60.8 62.0 61.1 59.1 Li2O/X2O 0.40 0.40 0.40 0.40 Al2O3+ZrO2 8.7 8.9 8.8 8.5 Nb2O5+TiO2+zro2+La2 315.7 16.0 15.8 15.3 XO 6.3 4.5 5.9 9.1 XO+X2O 17.2 15.6 16.8 19.7 Ag 0.232 0.257 0.239 0.257 Cl 0.328 0.353 0.344 0.340 Br 0.211 0.203 0.199 0.137 CuO 0.0100 0.0100 0.0100 0.0100 Table I (continued) SiO2 41.97 42.23 41.95 41.41 B2O3 17.28 19.30 19.73 18.78 Al23 5.80 3.00 6.19 6.11 Zr2 2.90 4.88 2.49 2.46 Li2O 4.54 4.30 4.38 4.63 Na2O 0.61 1.23 1.25 0.62 K2O 5.08 5.13 5.24 5.18 CaO - 2.22 2.27 La2O3 3.22 3.30 Nb25 10.43 10.52 10.76 10.62 TiO2 4.39 3.95 2.43 3.99 SrO 6.10 - - 6.21 BaO 0.90 SiO2+B2O3 59.2 61.5 61.7 60.2 Li2O/X2O 0.44 0.40 0.40 0.44 Al2O3+ZrO2 8.7 7.9 8.7 8.6 Nb2O5+TiO2+zro2+La2o3 17.7 22.6 19.0 17.1 XO 7.0 2.2 2.3 6.2 XO+X2O 17.2 12.9 13.2 16.6 Ag 0.145 0.190 0.190 0.169 Cl 0.240 0.330 0.335 0.279 Br 0.156 0.156 0.157 0.144 CuO 0.0130 0.0110 0.0110 0.0100 Table I (continued) SiO2 41.41 41.15 41.76 _ 42.75 B2O3 18.78 18.17 19.00 18.21 A123 6.11 6.07 6.16 6.13 Zr2 2.46 2.45 2.48 2.47 Li2O 4.63 4.60 4.69 4.66 Na2O 0.62 0.62 0.62 0.62 K2o 5.18 5.14 4.87 4.84 CaO
Nb25 10.62 10.55 8.03 8.04 TiO2 3.99 5.08 6.12 6.09 SrO 6.21 6.17 6.26 6.23 SiO2+B2O3 60.2 59.3 60.8 61.0 Li2O/X2O 0.44 0.44 0.46 0.46 A12O3+ZrO2 8.6 8.5 8.6 8.6 Nb2O5+TiO2+zro2+Lazo3 17.1 18.1 16.6 16.5 XO 6.2 6.2 6.3 6.2 XO+X2O 16.6 16.5 16.4 16.4 Ag 0.142 0.144 0.192 0.163 Cl 0.238 0.240 0.320 0.320 Br 0.186 0.178 0.180 0.180 CuO 0.0130 0.0130 0.0100 0.0100 -Table I (continued) SiO2 42.58 42.58 42.58 42.58 B2O3 17.27 17.27 17.27 17.27 Al23 5.87 5.87 5.87 5.87 Zr2 2.93 2.93 2.93 2.93 Li2O 4.89 4.89 4.89 4.89 Na2O 0.62 0.62 0.62 0.62 K2O 4.67 4.67 4.67 4.67 CaO
Nb25 10.55 10.55 10.55 10.55 TiO2 4.44 4.44 4.44 4.44 SrO 6.17 6.17 6.17 6.17 SiO2+B2O3 59.9 59.9 59.9 59.9 Li2o/X2O 0.48 0.48 0.48 0.48 Al2O3+ZrO2 8.8 8.8 8.8 8.8 Nb2O5+TiO2+zro2+La2o3 17.9 17.9 17.9 17.9 XO 6.2 6.2 6.2 6.2 XO+X2O 16.4 16.4 16.4 16.4 Ag 0.204 0.150 0.151 0.151 Cl 0.330 0.267 0.284 0.286 Br 0.167 0.167 0.149 0.153 CuO 0.0130 0.0140 0.1400.0140 As2O3 - - 0.15 SnO2 - 0.20 -Table I (continued) SiO2 _ 42.58 42.58 42.58 42.15 B2O3 17.27 17.27 17.27 17.08 Al23 5.87 5.87 5.87 5.70 Zr2 2.93 2.93 2.93 2.91 Li2O 4.89 4.89 4.89 4.87 Na2O 0.62 0.62 0.62 0.61 K2O 4.67 4.67 4.67 4.63 CaO - - - -Nb25 10.55 10.55 10.55 10.40 TiO2 4.44 4.44 4.44 4.39 SrO 6.17 6.17 6.17 6.25 2 23 59.9 59.9 59 9 59.2 Li2O/X2O 0.48 0.48 0.48 0.48 A12O3+ZrO2 8.8 8.8 8.8 8.6 Nb2O5+TiO2+zro2+La2o3 17.9 17.9 17.9 17.7 XO 6.2 6.2 6.2 6.3 XO+X2O 16.4 16.4 16.4 16.4 Ag 0.149 0.137 0.149 0.144 Cl 0.227 0.278 0.271 0.232 Br 0.168 0.168 0.163 0.155 CuO 0.0140 0.0100 0.0140 0.0170 Sb2O3 0.12 0.17 0.17 0.40 Table I ( continued ) SiO2 42.15 42.15 42.15 42.15 B2O3 17.08 17.08 17.08 17.08 Al23 5.70 5.70 5.70 5.70 Zr2 2.91 2.91 2.91 2.91 Li2O 4.87 4.87 4.87 4.87 Na2O 0.61 0.61 0.61 0.61 K2O 4.63 4.63 4.63 4.63 CaO - - - -Nb25 10.40 10.40 10.40 10.40 TiO2 4.39 4.39 4.39 4.39 SrO 6.25 6.25 6.25 6.25 SiO2+B2O3 59.2 59.2 59.2 59.2 Li2O/X2O 0.48 0.48 0.48 0.48 Al2O3+ZrO2 8.6 8.6 8.6 8.6 Nb2O5+TiO2+zro2+La2o3 17.7 17.7 17.7 17.7 XO 6.3 6.3 6.3 6.3 XO+X2O 16.4 16.4 16.4 16.4 Ag 0.147 0.147 0.146 0.146 Cl 0.232 0.203 0.258 0.230 Br 0.159 0.158 0.159 0.154 CuO 0.0200 0.0200 0.0200 0.0230 Sb23 0.40 0.52 0.50 0.54 - -18- 133376~
Table I (continued) SiO2 42.15 42.15 41.57 40.76 B2O3 17.08 17.08 21.12 19.17 2 3 5.70 5.70 5.80 4.01 Zr2 2.91 2.91 2.34 7.27 Li2O 4.87 4.87 2.27 4.26 Na2O 0.61 0.61 1.17 1.22 K2o 4.63 4.63 3.57 5.09 CaO - - 2.13 2.21 La2O3 - - 6.18 3.20 Nb25 10.40 10.40 10.08 10.45 TiO2 4.39 4.39 3.79 2.36 SrO 6.25 6.25 - -SiO2+B2O3 59.2 59.2 62.7 59.9 Li2O/X2O 0.48 0.48 0.32 0.40 Al2O3+ZrO2 8.6 8.6 8.1 11.3 Nb2O5+TiO2+zro2+La2 3 17.7 17.7 22.4 23.3 XO 6.3 6.3 2.1 2.2 XO+X2O 16.4 16.4 9.1 12.8 Ag 0.145 0.142 0.166 0.190 Cl 0.235 0.249 0.320 0.320 Br 0.160 0.159 -0.180 0.156 CuO 0.0230 0.0230 0.0120 0.0110 Sb23 0.54 0.49 `
Table I (continued) SiO2 41.3939.41 39.27 42.15 B2O3 27.6120.71 18.46 17.08 Al23 9.585.81 5.79 5.70 Zr2 - 2.34 2.33 2.91 Li2O 2.490.94 1.13 4.87 Na2O 1.291.18 1.17 0.61 K2O 3.9312.00 14.28 4.63 CaO 1.172.13 2.12 La23 1.703.10 3.09 Nb25 8.3210.11 10.07 10.40 TiO2 2.502.28 2.27 4.39 SrO _ _ _ 6.25 SiO2+B2O3 69.0 60.1 57.7 59.2 Li2O/X2O 0.320.07 0.07 0.48 Al2O3+ZrO2 9.6 8.2 8.1 8.6 Nb2O5+TiO2+zro2+La2o3 12.5 17.8 17.8 17.7 XO 1.2 2.1 2.1 6.3 XO+X2O 8.9 16.2 18.7 16.4 Ag 0.1900.257 0.253 0.147 Cl 0.2400.333 0.355 0.219 Br 0.1500.148 0.152 0.145 CuO 0.0120 0.0100 0.0100 0.0170 Sb23 - _ _ 79 Table I (continued) SiO2 _ 42.15 42.15 B2O3 17.08 17.08 23 5.70 5.70 Zr2 2.91 2.91 Li2O 4.87 4.87 Na2O 0.61 0.61 K2O 4.63 4.63 Nb25 10.40 10.40 i2 4.39 4.39 SrO 6.25 6.25 SiO2+B2O3 59.2 59.2 Li2O/X2O 0.48 0.48 Al2O3+ZrO2 8.6 8.6 Nb2O5+TiO2+zro2+La2o317.7 17.7 XO 6.3 6.3 XO+X2O 16.4 16.4 Ag 0.144 0.123 Cl 0.220 0.235 Br 0.142 0.160 CuO 0.0170 0.0235 23 0.70 0.39 Samples of glasses prepared from the compositions of Table I were placed in an electric furnace for a specific heat treatment (HT). Temperature ~in C) and time of heat treatment (in minutes) are reported on Table II. Generally, a temperature between about 580 and 640C for times between about five minutes to two hours have been found satisfactory to obtain the desired optical properties. After heat treatment, the samples are ground and polished to a thick-ness of 2 mm for properties measurement.
Table II gives also the photochromic performances, the color, the refractive index (nD), the Abbe number (v), the density (Den), and the viscosity (Vis) at the l33376a devitrification liquidus of the glasses. Two glass melts crystallized (devitrified) upon cooling, thereby resulting in an opaque glass body.
_ The color of the glasses is expressed as the tri-chromatic coordinates (x,y) defined by the C.I.E. colori-metric system of 1931 which uses the C illuminant. This colorimetric system and the light source are explained by A. C. Hardy in the Handbook of Colorimetry, Technology Press, M.I.T., Cambridge, Massachusetts (1936).
The color of the darkened state (x20, Y20) is deter-mined after a 20-minute exposure at 25C to a commercially-available ultraviolet light termed "black-light-blue". The corresponding luminous transmission is reported as TD20.
The luminous transmissions representing the behavior of the glasses under an actinic radiation similar to sunlight have been measured with eguipment called "Solar-Simulator," which equipment is described in U. S. Patent No. 4,190,451.
In Table II:
To is the luminous transmission of the glass in the clear state (unexposed).
TD15 (25C) is the luminous transmission after darkening 15 minutes in the simulated sunlight source at 25C.
TD15 (40C) is the luminous transmission after darkening 15 minutes in the simulated sunlight source at 40C.
TF5 (25C) is the luminous transmission after fading 5 minutes after removal from the simulated sunlight source at 25C.
vTD15 (25-40C) is the difference between transmissions after darkening 15 minutes in the simulated sunlight source at 25 and 40C.
The measurements of the refractive index and Abbe number are made by the usual methods on annealed samples.
The density is measured by the immersion method and expressed in g/cm3.
13337~
The liquidus temperature or upper crystallization temperature is determined with a gradient furnace. The duration of heat treatment is 17 hours; the presence of crystals is detected by using an optical microscope. The viscosity (expressed in poises) corresponding to the liquidus temperature is measured with a rotating viscosi-meter.
Table II
To 91.5 90.6 90.3 90.8 89.8 TD15 (25C) 26.8 22.3 24.2 31.2 32.5 TD15 (40C) 43.8 40.6 40.4 45.6 49.3 TF5 (25C) 61.2 59.0 56.5 57.2 69.6 vTD15 (25-40C)17.0 18.3 16.2 14.4 16.8 nD 1.588 1.585 1.585 1.589 1.589 v 47.50 47.00 46.70 47.10 44.00 Den. 2.65 2.61 2.63 2.71 Vis. 400 350 Table II (continued) To 90.5 89.5 89.2 89.7 88.5 TD15 (25C) 32.0 39.1 28.3 34.2 38.3 TD15 (40C) 51.9 55.1 44.7 53.4 59.2 TF5 (25C) 63.2 67.8 65.5 71.4 75.6 vTD15 (25-40C)19.9 16.0 16.4 19.2 20.9 nD 1.603 1.585 1.594 1.594 1.599 v 43.00 46.60 45.00 45.00 43.00 Den. 2.68 2.62 2.68 2.68 Vis. >350 200 500 500 >500 ~.
Table II Icontinued) HT 620-15 620-15 610-15 610-15 610-15_ D20 ~ ~ 40.95 40.7 41.59 x - - 0 3258 0.3187 0.3485 Y20 ~ ~ 0.3244 0.3214 0.3384 To 89.2 87.7 90.2 90.2 85.9 TD15 (25C) 23.0 29.8 23.9 30.5 23.7 TD15 (40C) 42.1 49.1 42.3 51.6 44.1 TF5 (25C) 61.6 67.4 58.0 67.7 63.5 vTD15 (25-40C)19.1 19.3 18.4 21.1 20.4 nD 1.596 1.596 1.601 1.601 1.601 v 44.00 44.00 44.00 44.00 44.00 Den. _ 2.62 2.69 2.69 2.69 Vis. >400 >400 >500 >500 >500 TD20 40.73 50.08 38.0440.3 39.4 x 0 3268 0.3370 0.3503- 0.3472 0.3505 Y20 0.3268 0.3343 0.3364 0.3356 0.3364 To 89.2 87.2 84.5 85.5 86.8 TD15 (25C) 26.0 36.1 22.3 28.4 24.6 TD15 (40C) 45.5 55.5 37 4 47 5 43 0 TF5 (25C) 65.3 70.4 60.1 66.5 62.4 vTD15 (25-40C)19.5 19.4 15.1 19.1 18.4 nD 1.601 1.601 1.601 1.601 1.600 v 44.00 44.00 44.00 44.00 44.00 Den. 2.69 2.69 2.69 2.69 2.70 Vis. >500 >500 >500 >500 >500 -24- 1~33760 Table II (continued) D20 41.9 39.5 40.2 42.6 43.4 x2o 0.3459 0.3466 0.34900.3452 0.3444 Y20 0.3365 0.3333 0.33680.3334 0.3355 To 84.5 85.4 85.4 86.0 85.0 TD15 (25C) 26.8 25.6 26.5 30.1 30.2 TD15 (40C) 43.9 42.6 45.0 48.3 47.8 TF5 (25C) 64.2 62.0 62.8 66.3 65.4 vTD15 (25-40C)17.1 17.0 18.5 18.2 17.6 nD 1.600 1.600 1.6001.600 1.600 v 44.00 44.00 44.0044.00 44.00 Den. 2.70 2.70 2.70 2.70 2.70 Vis. >500 >500 >500 >500 >500 TD20 43.9 C _ C
X20 0.3449 R _ R
Y20 0.3358 y _ y To 85.6 S 90.4 S 87.1 TD15 (25C) 32.5 T 51.6 T 18.0 TD15 (40C) 49.4 A 71.7 A 28.1 TF5 (25C) 66.5 L 81.5 L 42.2 vTD15 (25-40C)16.9 L 20.1 L 10.1 nD 1.600 I 1.602 I 1.565 v 44.00 Z 44.30 Z 47.00 Den. 2.70 E 2.69 E 2.58 Vis. ~500 D <100 D
-" 1333760 Table II (continued) HT _600-15 610-15 610-15 610-15 TD20 23.15 23.31 44.71 X20 _ 0.3303 0.3285 0.3284 Y20 _ 0.3048 0.3016 0.3196 To 89.9 85.2 82.2 84.3 TD15 (25C) 40.8 14.6 17.5 46.5 TD15 (40C) 42.0 22.6 23.2 48.0 TF5 (25C) 48.6 43.9 41.2 60.1 vTD15 (25-400C) 1.2 8.0 5.7 1.5 nD 1.572 1.600 1.600 1.600 v 47.70 44.00 44.00 44.00 Den. 2.62 2.70 2.70 2.70 Vis. 260 >500 >500 >500 Examples 1 to 5 are representative of compositions leading to photochromic glasses which are gray in the darkened state and which contain one or more divalent metals or alkaline-earths.
Examples 6 and 7 illustrate compositions of gray photochromic glasses in the darkened state which contain La203 .
Examples 8 to 14 represent photochromic glasses which have a similar base composition but different Ag, Br, Cl and CuO contents.
Examples 15 and 16 represent brown photochromic glasses in the darkened state, containing As2O3 and SnO2, respectively.
Examples 17 to 26 deal with brown photochromic glasses in the darkened state based on Sb2O3 and obtained from variable Ag, Br, Cl, CuO, and Sb2O3 amounts.
The color of those glasses can be compared to Example 14 color which is representative of a gray photochromic glass.
, Examples 8, 12, 14, 20, and 24 illustrate preferred embodiments of the invention, not only for the photochromic properties, but also for the overall physical and chemical characteristics.
Examples 27 to 34 represent glasses obtained from compositions which are not in the prescribed ranges of the invention .
Example 27 shows the negative effect of the (XO + X2O) sum on the glass stability against devitrification.
Example 28 is outside the ZrO2 claimed range. Further-more, the impact of the sum (ZrO2 + Al2O3) on the liquidus viscosity can be observed by comparing this Example to Examples 6 and 7. Example 28 shows a liquidus viscosity lower than 100 poises which does not allow the use of conventional pressing techniques.
Example 29 is outside B2O3 and Al2O3 claimed ranges.
The negative effect of the (SiO2 + B2O3) sum on the glass stability appears by comparison with Examples 6 and 7.
Examples 30 and 31 illustrate the effect of Li2O, K2O, and Li2O/X2O. Both of them show a faded transmission well below 55%.
Examples 32 and 33 illustrate the effect of a high Sb2O3 amount. The faded transmission is well below 55%
and, consequently, below the faded transmission of the glasses according to the invention containing Sb2O3 (TF5 >60%).
Example 34 shows the effect of a small Ag content.
The faded transmission is greater than 60%, but the glass does not darken enough.
This last parameter reflects the temperature dependence of the glasses according to the invention and in relation with parameters (1), (2), and (3), describes the optical characteristics of the lens over the extent of the 20 to 40C temperature range. Furthermore, the color character-istics of the lens in the clear state as well as in the darkened state are described by the trichromatic coordinates which will be explained hereinafter.
The above optical and photochromic properties of the present glasses are obtained in the alkali, aluminoboro-silicate composition family which contain niobium oxide.
In contrast to the photochromic glasses with an index of refraction of 1.523, the compositions described in this invention must necessarily contain oxides which contribute strongly to the index of refraction such as La2O3, Nb2O5, TiO2, CaO, SrO, and BaO in appreciable quantities when they are present in the composition in order to satisfy the above-mentioned criteria.
The base glass compositions consist essentially, expressed in terms of weight percent on the oxide basis, of:
SiO233-50 MgO 0-5 B2O315-25 CaO 0-5 SiO2+B2O358-66 SrO 0-10 Al2O3 2-9 BaO 0-10 Zr2 1-5 ZnO 0-5 Al2O3+ZrO2 4-10 MgO+CaO+SrO+BaO+ZnO 1-15 (XO) Li2O1.5-6 X2O+XO 10-24 Na2O0-4 La23 0-5 Li2O+Na2O+K2O 7-16 (X2O) TiO2 2 8 Li2o/x2o 0.20-0.50 Zro2+Tio2+Nb2os+La2o3 14-23 The preferred base glasses consist essentially of:
~4~ 1 3 3 3 7 ~ 0 SiO2 36-48 . MgO 0 B2O3 15-20 CaO 0 SiO2+B2O3 57-63 SrO 2-8 Al2O3 5-8 BaO 0 Zr2 1-4 ZnO 0 Al2O3+ZrO2 6-10 MgO+CaO+SrO+BaO+ZnO 2-9 (XO) Li2O 2-5.5 X2O+XO 10-20 Na2O 0.3-2.5 La23 K2O 3-8 Nb25 8 14 Li2O+Na2O+K2O 8-12 (X2O) TiO2 2 7 i O/X O 0 35-0.50 ZrO2+TiO2+Nb2O5 2 3 In addition to the composition of the base glass, the obtaining of photochromic properties such as are defined above requires the introduction of photochromic elements in the following proportions, expressed in terms of weight percent as analyzed in the glass:
Ag 0.130-0.280 Br 0.130-0.220 Ag+Br >0.270 Cl 0.170-0.360 CuO 0.0070-0.0350 The preferred proportions consisting essentially of:
Ag 0.135-0.180 8r 0.140-0.170 Ag+Br >0.280 Cl 0.200-0.300 CuO 0.0120-0.0300 Chlorine is used in quantities of 0.17-0.36%, prefera-bly 0.2-0.3%, as analyzed in weight percent in the glass.
It is an indispensable element which, when present in the correct proportions, permits the desired photochromic performance to be obtained. Its inclusion at too low a level leads to glasses exhibiting insufficient darkening, ~5~ 1333760 `_ whereas too high a content decreases the fading rate and the sensitivity of the glass to visible light.
The CuO content is 0.0070-0.0350, preferably 0.0120-0.0300, as analyzed in weight percent in the glass. CuO
acts as a "sensitizer" of silver halides and, therefore, its level in the glass must be carefully controlled. Below 0.0070%, the darkening of the glass is insufficient. On the other hand, above 0.030%, the temperature dependence of the glass becomes unacceptable.
The limits of the above-specified ranges for the constituents of the base glass are equally crucial in order to obtain glasses exhibiting good melting and forming capability, and possessing the chemical and physical properties, e.g., strengthening by chemical and/or physical tempering and good durability, demanded of glasses to be utilized in optical and ophthalmic applications, as well as the required photochromic behavior. More specifically, the viscosity at the liquidus temperature must be sufficient to permit pressing employing conventional forming techniques, i.e., a liquidus viscosity equal to or greater than about 200 poises.
SiO2 and B2O3 constitute the basic components of this type of glass. Their sum determines the quantity of other oxides and influences the devitrification characteristics.
It will be greater than 58% and lower than 66%. This condition is not sufficient to get the requested photo-chromic performances. The aptitude to precipitate silver halides, in an appropriate temperature range, depends on the amount of B2O3. It must not be lower than 15%. It is also known that B2O3 imparts a negative effect on the glass chemical durability and therefore the maximal content is fixed at 25% and preferably 20%.
Al2O3 is important because it affects the ability to retain in the glass Ag, Br, and Cl. For that reason, 2% at least, will be present and preferably at least 5%. In addition, Al2O3 stabilizes the glass against the natural -6- 13337~
tendency of these glasses to phase separation and as ZrO2, Al2O3 improves the chemical durability of the glass.
Furthermore, A12O3 increases considerably the glass viscosity which is favorable for the viscosity at the liquidus.
Zr2 improves the durability against alkaline attack and 1% at least must be present. It contributes signifi-cantly to the refractive index but also, increases quickly the crystallization characteristics of the glass. There-fore, a maximum of 5% will be present in the glass. It hasbeen observed that in high alumina glasses, the ZrO2 amount must be limited to avoid devitrification. Thus, the sum (Al2O3 + ZrO2) should be between 4 and 10%, and preferably between 6 and 10%.
Along with their small contribution to the density of the glass, the alkalies (Li2O, Na2O, K2O) are necessary to obtain the desired photochromism.
Among the alkalies, Li2O makes it possible to obtain the desired fading rate. The glass will contain at least 1.5% Li2O and preferably at least 2%. However, it decreases considerably the viscosity and increases the tendency to devitrification and phase separation. The maximum content is 6%, and preferably 5.5%.
Na2O is favorable to increase the mechanical strength which can be obtained by chemical strengthening. Conse-quently, the glasses will contain preferably at least 0.3%
Na2O. Due to its negative effect on the fading rate, a maximum of 4% will be used.
K2O is used in conjunction with Li2O at 2 to 9 wt. %
and preferably at 3 to 8 wt. %. In fact, as already mentioned, Li2O makes it possible to obtain fast fading glasses. However, inasmuch as the photochromic behavior is the result of two opposite mechanisms occurring simultane-ously (darkening and thermal fading), a too high fading rate will lead generally to a low darkening glass. K2O
enables one to get dark glasses without affecting too much the fading rate when present at 2 to 9%.
In a general way, the combination of the three alkali oxides is preferred. In this case, as mentioned previously, the following conditions should be satisfied:
7 < X O < 16 0.20 < Li2O/X2O < 0.6 with X2O = Li2O + Na2O + K2O.
The main contributor to the refractive index is Nb2O5.
Its effect on index is close to TiO2 but it is not as powerful as TiO2 to increase the glass dispersion. Further-more, it is equivalent to Al2O3 for the photochromic performances.
Nb2O5 must be present at a level of at least 8%.
However, being very expensive, a maximum of 16% and prefer-ably of 14% will be used.
TiO2 has no specific effect on the photochromic properties. At least 2% will be introduced in the glass.
High TiO2 content would impart to the glass an undesirable yellow coloration and would enhance the tendency to phase separation. For those reasons, the TiO2 content will not exceed 8% and preferably will be lower or equal to 7%.
In order to increase the refractive index, oxides such as: MgO, CaO, SrO, BaO, ZnO, and Li2O3 can also be added to the base glass. Among the divalent oxides, MgO and CaO
have a small contribution to the density but also to the refractive index. However, although the desired photo-chromic performances can be obtained with those oxides, SrO
will be preferred according to the invention. SrO
stabilizes the glass toward devitrification and phase separation. Consequently, SrO will be present in the glass at a level equal to or greater than 2% and lower than 8%.
To satisfy the constraints on refractive index and on density, the sum of divalent oxides (MgO + CaO + SrO + BaO
+ ZnO = XO) must meet the following condition:
1 < XO < 15 preferably 2 < XO < 12 and most particularly 2 < XO < 9.
1~33760 Furthermore, in presence of alkalies (Li2O, Na2O, K2O) and to have a glass stable against devitrification, the sum (X2O+XO) must fulfill the condition: 10 < X2O + XO < 24.
Finally, La2O3 not only strongly increases the refrac-tive index but also the density. The glass will notcontain more than 5% and preferably it will be absent from its composition.
With the limitations above mentioned and taking into account the required characteristics, the oxides having a large contribution to the refractive index such as ZrO2, TiO2, Nb2O5, and La2O3 must satisfy in a general way the condition:
r2 + TiO2 + Nb2Os + La23 < 23 The compositions which meet the conditions above mentioned, lead to glasses displaying all the optical and photochromic characteristics described in this invention.
The natural color of the glasses is, in the clear or unexposed state, slightly yellow or green and, in the darkened state, gray or brown-gray.
The glasses according to the invention can also be brown in the darkened state. Generally, and as described in prior art patents, to obtain a brown tint at darkening, noble metals such as Pd and Au, are added.
The brown photochromic glasses according to the invention, contain elements such as Sb2O3, AS2O3, and/or SnO2 .
For a given composition and to get a significant coloration, the sum of these oxides must be equal, at least, to 0.10%. However, it will be lower than 1% because they are also powerful redox agents. The values given are in weight percentage as analyzed in the glass.
According to a preferred embodiment of the invention, antimony oxide will be used to get a brown glass at darken-ing. The maximal Sb2O3 content is 0.65%. Above that value, Sb2O3 imparts to the glass a too strong yellow coloration in the clear state, i.e., the transmission To would be too low. In order to avoid undesirable effects _ -9- 1333760 (too reduced glass, Ag metallic precipitation), Sb2O3 will be used with preferred compositions for Ag, Cl, Br, CuO as defined previously.
Those "colorants" give to the glass in the clear _ state, a slightly yellow tint. If necessary, it can be attenuated by addition of colorant oxides such as Er2O3, CoO, ~r Nd2O3.
Prior Art U. S. Patent No. 3,630,765 discloses photochromic glasses exhibiting refractive indices higher than 1.54.
The essence of the inventive glasses comprised adding 10-50% by weight Ta2O5 to silver halide-containing, alkali metal aluminoborosilicate base glass compositions to raise the refractive index thereof. No mention is made of Nb2O5, TiO2, and/or ZrO2.
U. S. Patent No. 3,703,388 is expressly directed to high refractive index photochromic glasses. The glasses -20 consisted essentially, in weight percent, of 15-75% La203, 13-65% B2O3, the sum La2O3 + B2O3 being at least 30%, with silver halides being present there. Various proportions of Nb2O5, TiO2, and ZrO2 are mentioned as optional components.
Nevertheless, the base glass compositions are far afield from those of the present invention.
U. S. Patent No. 3,999,996 is drawn to silver halide-containing photochromic glasses demonstrating refractive indices >1.60 having base glass compositions consisting essentially, in weight percent, of:
SiO2 10-20 ZrO2 0.5-3 B2O3 15-23 TiO2 0.2-3 PbO 26-30 K2O 0.1-2 ZnO 3-5 Na2O 0.1-2 La2O3 6-10 Li2O 0.1-4 Such compositions are very remote from those of the present invention .
-lO- 1333760 U. S. Patent No. 4,149,896 is concerned with silver halide-containing photochromic glasses exhibiting refractive indices in excess of 1.60 having base compositions consist-ing essentially, in weight percent, of:
SiO2 5 30 Zr2 0-6 B2O3 7-35 i 2 3 PbO 6-26 K2O 0-2 ZnO 0-15 Na2O 0-2 La23 12-30 Li2O 0-4 A12O3 12-25 Bi2O3 and/or Ta2O5 and/or Nb2O3 and/or WO3 0-5 Such compositions are quite removed from the ranges of the present invention.
U. S. Patent No. 4,486,541 describes silver halide-containing photochromic glasses exhibiting refractive indices 21.59 claiming base compositions consisting essen-tially, in weight percent, of:
SiO232-47 wo3 0-1 B2O314.5-27 MgO 0-1 P2O50-11 CaO 0-6 SiO2+B2O3+p2o558-71 SrO 0-24 A1230-0.4 PbO 0.5-12 Zr21.5-10 TiO2 0.5-8 La2O30-23 Li2O 0.5-6 Nb25 0-2 Na2O 0-4 Ta2O50-18 R2O 6-12 wherein Li2O+Na2O+R2O 6.5-15 and l2o3+zro2+La2O3+Nb2Os+Ta2O5~WO3 2-25 and wherein MgO+CaO+SrO 2-24 and wherein La2O3 SrO PbO TiO2 Nb2O5 ZrO2 WO3 Ta2O5 12 34 Such compositions are outside of those of the present invention at least with respect to A12O3, Nb2O5, and PbO.
U. S. Patent No. 4,686,196 presents silver halide-containing photochromic glasses demonstrating refractive indices 21.59 claiming base compositions consisting essen-tially, in weight percent, of:
SiO2 42-56 SrO 0-3 B2O3 11-18 BaO 0-6 Al2O3 0-5 ZnO 0-2 2+B2O3+Al2O3 55-75 MgO+CaO+SrO+BaO+ZnO 3-12 Li2O 3-9 TiO2 3.06-6.74 Na2O 0-7.98 Zr2 2-11 K2O 0-8.22 Nb2O5 2.28-8 Li2O+Na2O+K2O 7-15 La23 0-3 MgO 3-12 PbO 0-2 CaO 0-3 r23 0-1 Such compositions are low in Nb2O5 and SrO and require the presence of MgO.
Description of Preferred Em~odiments The following examples, which must be deemed illustra-tive only and not limitative, describe the invention.
Compositions are given in Table I. The quantities of components are expressed in parts-by weight on the oxide basis. Taking into account that the total of components is equal to or close to 100, the given values can be considered as weight percent.
As the cation(s) to which halogens are bound are not known, and because they are present in small amounts, they are reported as chlorine and bromine in agreement with the usual practice. Silver, present also in small amounts, is given as the metal.
The reported values for Ag, Cl, Br, CuO, Sb203, and SnO2 are, in general, as analyzed in the glasses, except if specifically mentioned otherwise.
Batches are prepared from raw materials, oxides, or ' other compounds which, when they are melted together, are converted into the desired oxides at the required level.
Chlorine and bromine are generally incorporated as halides of alkali metals. Components used to tint the glass are generally added as oxides or compounds of the metal.
Ingredients of the raw materials batch are weighed and carefully mixed (ballmilled) to help in achieving homogene-ity of the melted glass. Then they are charged into a _ platinum crucible, that crucible is introduced into a furnace heated by Joule effect, and the batch is melted at 1350C for about 3 hours. After casting to form a slab, the glass is annealed at about 450C.
Table I
SiO2 39.64 40.42 39.82 38.48 B2O3 21.20 21.62 21.30 20.58 Al23 6.21 6.33 6.24 6.03 ZrO2 2.50 2.55 2.51 2.43 Li2O 4.40 4.48 4.42 4.27 Na2O 1.26 1.28 1.26 1.22 K2O 5.26 5.36 5.28 5.10 CaO - 2.32 Nb25 10.79 11.00 10.84 10.47 TiO2 2.43 2.48 2.44 2.36 SrO 6.31 2.14 4.23 BaO - - - 9.06 ZnO - - 1.66 SiO2+B2O3 60.8 62.0 61.1 59.1 Li2O/X2O 0.40 0.40 0.40 0.40 Al2O3+ZrO2 8.7 8.9 8.8 8.5 Nb2O5+TiO2+zro2+La2 315.7 16.0 15.8 15.3 XO 6.3 4.5 5.9 9.1 XO+X2O 17.2 15.6 16.8 19.7 Ag 0.232 0.257 0.239 0.257 Cl 0.328 0.353 0.344 0.340 Br 0.211 0.203 0.199 0.137 CuO 0.0100 0.0100 0.0100 0.0100 Table I (continued) SiO2 41.97 42.23 41.95 41.41 B2O3 17.28 19.30 19.73 18.78 Al23 5.80 3.00 6.19 6.11 Zr2 2.90 4.88 2.49 2.46 Li2O 4.54 4.30 4.38 4.63 Na2O 0.61 1.23 1.25 0.62 K2O 5.08 5.13 5.24 5.18 CaO - 2.22 2.27 La2O3 3.22 3.30 Nb25 10.43 10.52 10.76 10.62 TiO2 4.39 3.95 2.43 3.99 SrO 6.10 - - 6.21 BaO 0.90 SiO2+B2O3 59.2 61.5 61.7 60.2 Li2O/X2O 0.44 0.40 0.40 0.44 Al2O3+ZrO2 8.7 7.9 8.7 8.6 Nb2O5+TiO2+zro2+La2o3 17.7 22.6 19.0 17.1 XO 7.0 2.2 2.3 6.2 XO+X2O 17.2 12.9 13.2 16.6 Ag 0.145 0.190 0.190 0.169 Cl 0.240 0.330 0.335 0.279 Br 0.156 0.156 0.157 0.144 CuO 0.0130 0.0110 0.0110 0.0100 Table I (continued) SiO2 41.41 41.15 41.76 _ 42.75 B2O3 18.78 18.17 19.00 18.21 A123 6.11 6.07 6.16 6.13 Zr2 2.46 2.45 2.48 2.47 Li2O 4.63 4.60 4.69 4.66 Na2O 0.62 0.62 0.62 0.62 K2o 5.18 5.14 4.87 4.84 CaO
Nb25 10.62 10.55 8.03 8.04 TiO2 3.99 5.08 6.12 6.09 SrO 6.21 6.17 6.26 6.23 SiO2+B2O3 60.2 59.3 60.8 61.0 Li2O/X2O 0.44 0.44 0.46 0.46 A12O3+ZrO2 8.6 8.5 8.6 8.6 Nb2O5+TiO2+zro2+Lazo3 17.1 18.1 16.6 16.5 XO 6.2 6.2 6.3 6.2 XO+X2O 16.6 16.5 16.4 16.4 Ag 0.142 0.144 0.192 0.163 Cl 0.238 0.240 0.320 0.320 Br 0.186 0.178 0.180 0.180 CuO 0.0130 0.0130 0.0100 0.0100 -Table I (continued) SiO2 42.58 42.58 42.58 42.58 B2O3 17.27 17.27 17.27 17.27 Al23 5.87 5.87 5.87 5.87 Zr2 2.93 2.93 2.93 2.93 Li2O 4.89 4.89 4.89 4.89 Na2O 0.62 0.62 0.62 0.62 K2O 4.67 4.67 4.67 4.67 CaO
Nb25 10.55 10.55 10.55 10.55 TiO2 4.44 4.44 4.44 4.44 SrO 6.17 6.17 6.17 6.17 SiO2+B2O3 59.9 59.9 59.9 59.9 Li2o/X2O 0.48 0.48 0.48 0.48 Al2O3+ZrO2 8.8 8.8 8.8 8.8 Nb2O5+TiO2+zro2+La2o3 17.9 17.9 17.9 17.9 XO 6.2 6.2 6.2 6.2 XO+X2O 16.4 16.4 16.4 16.4 Ag 0.204 0.150 0.151 0.151 Cl 0.330 0.267 0.284 0.286 Br 0.167 0.167 0.149 0.153 CuO 0.0130 0.0140 0.1400.0140 As2O3 - - 0.15 SnO2 - 0.20 -Table I (continued) SiO2 _ 42.58 42.58 42.58 42.15 B2O3 17.27 17.27 17.27 17.08 Al23 5.87 5.87 5.87 5.70 Zr2 2.93 2.93 2.93 2.91 Li2O 4.89 4.89 4.89 4.87 Na2O 0.62 0.62 0.62 0.61 K2O 4.67 4.67 4.67 4.63 CaO - - - -Nb25 10.55 10.55 10.55 10.40 TiO2 4.44 4.44 4.44 4.39 SrO 6.17 6.17 6.17 6.25 2 23 59.9 59.9 59 9 59.2 Li2O/X2O 0.48 0.48 0.48 0.48 A12O3+ZrO2 8.8 8.8 8.8 8.6 Nb2O5+TiO2+zro2+La2o3 17.9 17.9 17.9 17.7 XO 6.2 6.2 6.2 6.3 XO+X2O 16.4 16.4 16.4 16.4 Ag 0.149 0.137 0.149 0.144 Cl 0.227 0.278 0.271 0.232 Br 0.168 0.168 0.163 0.155 CuO 0.0140 0.0100 0.0140 0.0170 Sb2O3 0.12 0.17 0.17 0.40 Table I ( continued ) SiO2 42.15 42.15 42.15 42.15 B2O3 17.08 17.08 17.08 17.08 Al23 5.70 5.70 5.70 5.70 Zr2 2.91 2.91 2.91 2.91 Li2O 4.87 4.87 4.87 4.87 Na2O 0.61 0.61 0.61 0.61 K2O 4.63 4.63 4.63 4.63 CaO - - - -Nb25 10.40 10.40 10.40 10.40 TiO2 4.39 4.39 4.39 4.39 SrO 6.25 6.25 6.25 6.25 SiO2+B2O3 59.2 59.2 59.2 59.2 Li2O/X2O 0.48 0.48 0.48 0.48 Al2O3+ZrO2 8.6 8.6 8.6 8.6 Nb2O5+TiO2+zro2+La2o3 17.7 17.7 17.7 17.7 XO 6.3 6.3 6.3 6.3 XO+X2O 16.4 16.4 16.4 16.4 Ag 0.147 0.147 0.146 0.146 Cl 0.232 0.203 0.258 0.230 Br 0.159 0.158 0.159 0.154 CuO 0.0200 0.0200 0.0200 0.0230 Sb23 0.40 0.52 0.50 0.54 - -18- 133376~
Table I (continued) SiO2 42.15 42.15 41.57 40.76 B2O3 17.08 17.08 21.12 19.17 2 3 5.70 5.70 5.80 4.01 Zr2 2.91 2.91 2.34 7.27 Li2O 4.87 4.87 2.27 4.26 Na2O 0.61 0.61 1.17 1.22 K2o 4.63 4.63 3.57 5.09 CaO - - 2.13 2.21 La2O3 - - 6.18 3.20 Nb25 10.40 10.40 10.08 10.45 TiO2 4.39 4.39 3.79 2.36 SrO 6.25 6.25 - -SiO2+B2O3 59.2 59.2 62.7 59.9 Li2O/X2O 0.48 0.48 0.32 0.40 Al2O3+ZrO2 8.6 8.6 8.1 11.3 Nb2O5+TiO2+zro2+La2 3 17.7 17.7 22.4 23.3 XO 6.3 6.3 2.1 2.2 XO+X2O 16.4 16.4 9.1 12.8 Ag 0.145 0.142 0.166 0.190 Cl 0.235 0.249 0.320 0.320 Br 0.160 0.159 -0.180 0.156 CuO 0.0230 0.0230 0.0120 0.0110 Sb23 0.54 0.49 `
Table I (continued) SiO2 41.3939.41 39.27 42.15 B2O3 27.6120.71 18.46 17.08 Al23 9.585.81 5.79 5.70 Zr2 - 2.34 2.33 2.91 Li2O 2.490.94 1.13 4.87 Na2O 1.291.18 1.17 0.61 K2O 3.9312.00 14.28 4.63 CaO 1.172.13 2.12 La23 1.703.10 3.09 Nb25 8.3210.11 10.07 10.40 TiO2 2.502.28 2.27 4.39 SrO _ _ _ 6.25 SiO2+B2O3 69.0 60.1 57.7 59.2 Li2O/X2O 0.320.07 0.07 0.48 Al2O3+ZrO2 9.6 8.2 8.1 8.6 Nb2O5+TiO2+zro2+La2o3 12.5 17.8 17.8 17.7 XO 1.2 2.1 2.1 6.3 XO+X2O 8.9 16.2 18.7 16.4 Ag 0.1900.257 0.253 0.147 Cl 0.2400.333 0.355 0.219 Br 0.1500.148 0.152 0.145 CuO 0.0120 0.0100 0.0100 0.0170 Sb23 - _ _ 79 Table I (continued) SiO2 _ 42.15 42.15 B2O3 17.08 17.08 23 5.70 5.70 Zr2 2.91 2.91 Li2O 4.87 4.87 Na2O 0.61 0.61 K2O 4.63 4.63 Nb25 10.40 10.40 i2 4.39 4.39 SrO 6.25 6.25 SiO2+B2O3 59.2 59.2 Li2O/X2O 0.48 0.48 Al2O3+ZrO2 8.6 8.6 Nb2O5+TiO2+zro2+La2o317.7 17.7 XO 6.3 6.3 XO+X2O 16.4 16.4 Ag 0.144 0.123 Cl 0.220 0.235 Br 0.142 0.160 CuO 0.0170 0.0235 23 0.70 0.39 Samples of glasses prepared from the compositions of Table I were placed in an electric furnace for a specific heat treatment (HT). Temperature ~in C) and time of heat treatment (in minutes) are reported on Table II. Generally, a temperature between about 580 and 640C for times between about five minutes to two hours have been found satisfactory to obtain the desired optical properties. After heat treatment, the samples are ground and polished to a thick-ness of 2 mm for properties measurement.
Table II gives also the photochromic performances, the color, the refractive index (nD), the Abbe number (v), the density (Den), and the viscosity (Vis) at the l33376a devitrification liquidus of the glasses. Two glass melts crystallized (devitrified) upon cooling, thereby resulting in an opaque glass body.
_ The color of the glasses is expressed as the tri-chromatic coordinates (x,y) defined by the C.I.E. colori-metric system of 1931 which uses the C illuminant. This colorimetric system and the light source are explained by A. C. Hardy in the Handbook of Colorimetry, Technology Press, M.I.T., Cambridge, Massachusetts (1936).
The color of the darkened state (x20, Y20) is deter-mined after a 20-minute exposure at 25C to a commercially-available ultraviolet light termed "black-light-blue". The corresponding luminous transmission is reported as TD20.
The luminous transmissions representing the behavior of the glasses under an actinic radiation similar to sunlight have been measured with eguipment called "Solar-Simulator," which equipment is described in U. S. Patent No. 4,190,451.
In Table II:
To is the luminous transmission of the glass in the clear state (unexposed).
TD15 (25C) is the luminous transmission after darkening 15 minutes in the simulated sunlight source at 25C.
TD15 (40C) is the luminous transmission after darkening 15 minutes in the simulated sunlight source at 40C.
TF5 (25C) is the luminous transmission after fading 5 minutes after removal from the simulated sunlight source at 25C.
vTD15 (25-40C) is the difference between transmissions after darkening 15 minutes in the simulated sunlight source at 25 and 40C.
The measurements of the refractive index and Abbe number are made by the usual methods on annealed samples.
The density is measured by the immersion method and expressed in g/cm3.
13337~
The liquidus temperature or upper crystallization temperature is determined with a gradient furnace. The duration of heat treatment is 17 hours; the presence of crystals is detected by using an optical microscope. The viscosity (expressed in poises) corresponding to the liquidus temperature is measured with a rotating viscosi-meter.
Table II
To 91.5 90.6 90.3 90.8 89.8 TD15 (25C) 26.8 22.3 24.2 31.2 32.5 TD15 (40C) 43.8 40.6 40.4 45.6 49.3 TF5 (25C) 61.2 59.0 56.5 57.2 69.6 vTD15 (25-40C)17.0 18.3 16.2 14.4 16.8 nD 1.588 1.585 1.585 1.589 1.589 v 47.50 47.00 46.70 47.10 44.00 Den. 2.65 2.61 2.63 2.71 Vis. 400 350 Table II (continued) To 90.5 89.5 89.2 89.7 88.5 TD15 (25C) 32.0 39.1 28.3 34.2 38.3 TD15 (40C) 51.9 55.1 44.7 53.4 59.2 TF5 (25C) 63.2 67.8 65.5 71.4 75.6 vTD15 (25-40C)19.9 16.0 16.4 19.2 20.9 nD 1.603 1.585 1.594 1.594 1.599 v 43.00 46.60 45.00 45.00 43.00 Den. 2.68 2.62 2.68 2.68 Vis. >350 200 500 500 >500 ~.
Table II Icontinued) HT 620-15 620-15 610-15 610-15 610-15_ D20 ~ ~ 40.95 40.7 41.59 x - - 0 3258 0.3187 0.3485 Y20 ~ ~ 0.3244 0.3214 0.3384 To 89.2 87.7 90.2 90.2 85.9 TD15 (25C) 23.0 29.8 23.9 30.5 23.7 TD15 (40C) 42.1 49.1 42.3 51.6 44.1 TF5 (25C) 61.6 67.4 58.0 67.7 63.5 vTD15 (25-40C)19.1 19.3 18.4 21.1 20.4 nD 1.596 1.596 1.601 1.601 1.601 v 44.00 44.00 44.00 44.00 44.00 Den. _ 2.62 2.69 2.69 2.69 Vis. >400 >400 >500 >500 >500 TD20 40.73 50.08 38.0440.3 39.4 x 0 3268 0.3370 0.3503- 0.3472 0.3505 Y20 0.3268 0.3343 0.3364 0.3356 0.3364 To 89.2 87.2 84.5 85.5 86.8 TD15 (25C) 26.0 36.1 22.3 28.4 24.6 TD15 (40C) 45.5 55.5 37 4 47 5 43 0 TF5 (25C) 65.3 70.4 60.1 66.5 62.4 vTD15 (25-40C)19.5 19.4 15.1 19.1 18.4 nD 1.601 1.601 1.601 1.601 1.600 v 44.00 44.00 44.00 44.00 44.00 Den. 2.69 2.69 2.69 2.69 2.70 Vis. >500 >500 >500 >500 >500 -24- 1~33760 Table II (continued) D20 41.9 39.5 40.2 42.6 43.4 x2o 0.3459 0.3466 0.34900.3452 0.3444 Y20 0.3365 0.3333 0.33680.3334 0.3355 To 84.5 85.4 85.4 86.0 85.0 TD15 (25C) 26.8 25.6 26.5 30.1 30.2 TD15 (40C) 43.9 42.6 45.0 48.3 47.8 TF5 (25C) 64.2 62.0 62.8 66.3 65.4 vTD15 (25-40C)17.1 17.0 18.5 18.2 17.6 nD 1.600 1.600 1.6001.600 1.600 v 44.00 44.00 44.0044.00 44.00 Den. 2.70 2.70 2.70 2.70 2.70 Vis. >500 >500 >500 >500 >500 TD20 43.9 C _ C
X20 0.3449 R _ R
Y20 0.3358 y _ y To 85.6 S 90.4 S 87.1 TD15 (25C) 32.5 T 51.6 T 18.0 TD15 (40C) 49.4 A 71.7 A 28.1 TF5 (25C) 66.5 L 81.5 L 42.2 vTD15 (25-40C)16.9 L 20.1 L 10.1 nD 1.600 I 1.602 I 1.565 v 44.00 Z 44.30 Z 47.00 Den. 2.70 E 2.69 E 2.58 Vis. ~500 D <100 D
-" 1333760 Table II (continued) HT _600-15 610-15 610-15 610-15 TD20 23.15 23.31 44.71 X20 _ 0.3303 0.3285 0.3284 Y20 _ 0.3048 0.3016 0.3196 To 89.9 85.2 82.2 84.3 TD15 (25C) 40.8 14.6 17.5 46.5 TD15 (40C) 42.0 22.6 23.2 48.0 TF5 (25C) 48.6 43.9 41.2 60.1 vTD15 (25-400C) 1.2 8.0 5.7 1.5 nD 1.572 1.600 1.600 1.600 v 47.70 44.00 44.00 44.00 Den. 2.62 2.70 2.70 2.70 Vis. 260 >500 >500 >500 Examples 1 to 5 are representative of compositions leading to photochromic glasses which are gray in the darkened state and which contain one or more divalent metals or alkaline-earths.
Examples 6 and 7 illustrate compositions of gray photochromic glasses in the darkened state which contain La203 .
Examples 8 to 14 represent photochromic glasses which have a similar base composition but different Ag, Br, Cl and CuO contents.
Examples 15 and 16 represent brown photochromic glasses in the darkened state, containing As2O3 and SnO2, respectively.
Examples 17 to 26 deal with brown photochromic glasses in the darkened state based on Sb2O3 and obtained from variable Ag, Br, Cl, CuO, and Sb2O3 amounts.
The color of those glasses can be compared to Example 14 color which is representative of a gray photochromic glass.
, Examples 8, 12, 14, 20, and 24 illustrate preferred embodiments of the invention, not only for the photochromic properties, but also for the overall physical and chemical characteristics.
Examples 27 to 34 represent glasses obtained from compositions which are not in the prescribed ranges of the invention .
Example 27 shows the negative effect of the (XO + X2O) sum on the glass stability against devitrification.
Example 28 is outside the ZrO2 claimed range. Further-more, the impact of the sum (ZrO2 + Al2O3) on the liquidus viscosity can be observed by comparing this Example to Examples 6 and 7. Example 28 shows a liquidus viscosity lower than 100 poises which does not allow the use of conventional pressing techniques.
Example 29 is outside B2O3 and Al2O3 claimed ranges.
The negative effect of the (SiO2 + B2O3) sum on the glass stability appears by comparison with Examples 6 and 7.
Examples 30 and 31 illustrate the effect of Li2O, K2O, and Li2O/X2O. Both of them show a faded transmission well below 55%.
Examples 32 and 33 illustrate the effect of a high Sb2O3 amount. The faded transmission is well below 55%
and, consequently, below the faded transmission of the glasses according to the invention containing Sb2O3 (TF5 >60%).
Example 34 shows the effect of a small Ag content.
The faded transmission is greater than 60%, but the glass does not darken enough.
Claims (6)
1. A photochromic glass having a refractive index greater than 1.585, an Abbe number greater than 42, a density lower than 2.80 g/cm3, a liquidus viscosity of a least 200 poises, and, at a thickness of 2 mm, exhibits photochromic properties of (I) a luminous transmission in the unexposed state greater than 84%, (II) a luminous transmission in the darkened state after 15 minutes exposure to actinic radiation at a temperature between 0°-25° C. of less than 40%, (III) a fading rate at 20°-25° C. such that five minutes after removal from the actinic radiation the glass has a luminous transmission of at least 55%, and (IV) a difference between the luminous transmissions of the darkened state over the temperature range 25°-40° C. of less than 23 points of transmission, said glass consisting essentially of:
(a) a base glass composition consisting essentially, expressed in terms of weight percent on the oxide basis, of SiO2 33-50 MgO 0-5 B2O3 15-25 CaO 0-5 SiO2+B2O3 58-66 SrO 0-10 Al2O3 2-9 BaO 0-10 ZrO2 1-5 ZnO 0-5 Al2O3+ZrO2 4-10 MgO+CaO+SrO+BaO+ZnO 1-15 (XO) Li2O 1.5-6 X2O+XO 10-24 Na2O 0-4 La2O3 0-5 K2O 2-9 Nb2O5 8-16 Li2O+Na2O+K2O 7-16 (X2O) TiO2 2-8 Li2O/X2O 0.20-0.50 ZrO2+TiO2+Nb2O5+La2O3 14-23 and (b) photochromic elements consisting essentially, as analyzed in weight percent, of Ag 0.130-0.280 Br 0.130-0.220 Ag+Br >0.270 Cl 0.170-0.360 CuO 0.0070-0.0350.
(a) a base glass composition consisting essentially, expressed in terms of weight percent on the oxide basis, of SiO2 33-50 MgO 0-5 B2O3 15-25 CaO 0-5 SiO2+B2O3 58-66 SrO 0-10 Al2O3 2-9 BaO 0-10 ZrO2 1-5 ZnO 0-5 Al2O3+ZrO2 4-10 MgO+CaO+SrO+BaO+ZnO 1-15 (XO) Li2O 1.5-6 X2O+XO 10-24 Na2O 0-4 La2O3 0-5 K2O 2-9 Nb2O5 8-16 Li2O+Na2O+K2O 7-16 (X2O) TiO2 2-8 Li2O/X2O 0.20-0.50 ZrO2+TiO2+Nb2O5+La2O3 14-23 and (b) photochromic elements consisting essentially, as analyzed in weight percent, of Ag 0.130-0.280 Br 0.130-0.220 Ag+Br >0.270 Cl 0.170-0.360 CuO 0.0070-0.0350.
2. A photochromic glass according to claim 1 wherein said base glass composition also contains about 0.1-1% total, as analyzed in weight percent, of at least one member of the group consisting of As2O3, Sb2O3, and SnO2.
3. A photochromic glass according to claim 2 wherein said member of the group consists of 0.10-0.65% Sb2O3.
4. A photochromic glass according to claim 1 wherein said base glass composition consists essentially of:
SiO2 36-48 MgO 0 B2O3 15-20 CaO 0 SiO2+B2O3 57-63 SrO 2-8 Al2O3 5-8 BaO 0 ZrO2 1-4 ZnO 0 Al2O3+ZrO2 6-10 MgO+CaO+SrO+BaO+ZnO 2-9 (XO) Li2O 2-5.5 X2O+XO 10-20 Na2O 0.3-2.5 La2O3 0 K2O 3-8 Nb2O5 8-14 Li2O+Na2O+K2O 8-12 (X2O) TiO2 2-7 Li2O/X2O 0.35-0.50 ZrO2+TiO2+Nb2O5+La2O3 15-23 and said photochromic elements consist essentially of:
Ag 0.135-0.180 Br 0.140-0.170 Ag+Br >0.280 Cl 0.200-0.300 CuO 0.0120-0.0300.
SiO2 36-48 MgO 0 B2O3 15-20 CaO 0 SiO2+B2O3 57-63 SrO 2-8 Al2O3 5-8 BaO 0 ZrO2 1-4 ZnO 0 Al2O3+ZrO2 6-10 MgO+CaO+SrO+BaO+ZnO 2-9 (XO) Li2O 2-5.5 X2O+XO 10-20 Na2O 0.3-2.5 La2O3 0 K2O 3-8 Nb2O5 8-14 Li2O+Na2O+K2O 8-12 (X2O) TiO2 2-7 Li2O/X2O 0.35-0.50 ZrO2+TiO2+Nb2O5+La2O3 15-23 and said photochromic elements consist essentially of:
Ag 0.135-0.180 Br 0.140-0.170 Ag+Br >0.280 Cl 0.200-0.300 CuO 0.0120-0.0300.
5. A photochromic glass according to claim 4 wherein said base glass composition also contains about 0.1-1% total, as analyzed in weight percent, of at least one member of the group consisting of As2O3, Sb2O3, and SnO2.
6. A photochromic glass according to claim 5 wherein said member of the group consists of 0.10-0.65% Sb2O3.
29.
29.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR8810269A FR2634752B1 (en) | 1988-07-29 | 1988-07-29 | PHOTOCHROMIC LENSES WITH HIGH REFRACTION INDEX |
| FR8810269 | 1988-07-29 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1333760C true CA1333760C (en) | 1995-01-03 |
Family
ID=9368932
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000593311A Expired - Fee Related CA1333760C (en) | 1988-07-29 | 1989-03-10 | High index photochromic glasses |
Country Status (13)
| Country | Link |
|---|---|
| US (1) | US4891336A (en) |
| EP (1) | EP0353834B1 (en) |
| JP (1) | JPH0248426A (en) |
| KR (1) | KR960015145B1 (en) |
| CN (1) | CN1023392C (en) |
| AR (1) | AR243486A1 (en) |
| BR (1) | BR8903740A (en) |
| CA (1) | CA1333760C (en) |
| DE (1) | DE68915222T2 (en) |
| ES (1) | ES2051999T3 (en) |
| FR (1) | FR2634752B1 (en) |
| HK (1) | HK148094A (en) |
| IN (1) | IN172239B (en) |
Families Citing this family (34)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR2653239B1 (en) * | 1989-10-12 | 1992-10-30 | Corning France | PHOTOCHROMIC LENSES WITH HIGH FAST REFRACTION INDEX. |
| US5039631A (en) * | 1990-01-11 | 1991-08-13 | Schott Glass Technologies, Inc. | Strengthenable, high non-nd lanthanoid-containing glasses |
| US5077240A (en) * | 1990-01-11 | 1991-12-31 | Schott Glass Technologies, Inc. | Strengthenable, high neodymium-containing glasses |
| US5324691A (en) * | 1990-04-10 | 1994-06-28 | Isuzu Glass Co., Ltd. | Glass composition |
| US5275979A (en) * | 1992-10-30 | 1994-01-04 | Corning Incorporated | Colored glasses and method |
| FR2701020B1 (en) * | 1993-02-01 | 1995-04-21 | Corning Inc | Photochromic lenses that darken to a pink tint. |
| JP2872899B2 (en) * | 1993-11-26 | 1999-03-24 | 株式会社オハラ | Optical glass |
| DE4408190C1 (en) * | 1994-03-11 | 1995-08-03 | Deutsche Spezialglas Ag | High-index phototropic glass |
| FR2717915B1 (en) * | 1994-03-22 | 1996-06-07 | Corning Inc | High index photochromic lenses. |
| JPH08171741A (en) * | 1994-12-19 | 1996-07-02 | Tdk Corp | Production of photochromic glass thin film and optical information medium and its reproducing method |
| DE19520016C2 (en) * | 1995-05-26 | 1997-04-30 | Ivoclar Ag | Photochromic dental materials |
| US5541142A (en) * | 1995-07-31 | 1996-07-30 | Corning Incorporated | Method of making a color filter by precipitation of Cu2 O from a glass matrix |
| US6399527B1 (en) * | 1998-09-22 | 2002-06-04 | Nippon Sheet Glass Co., Ltd. | Glass composition and substrate for information recording medium |
| US6711917B2 (en) | 2000-09-15 | 2004-03-30 | Guardian Industries Corporation | Photochromic float glasses and methods of making the same |
| CN100354221C (en) * | 2001-01-11 | 2007-12-12 | 日本板硝子株式会社 | Mother material glass composition for refractive index distribution lens glass |
| KR20020074928A (en) * | 2001-03-22 | 2002-10-04 | 김서영 | A natural glass using photochromism principle |
| US7087542B2 (en) * | 2001-06-06 | 2006-08-08 | Kabushiki Kaisha Ohara | Optical glass |
| JP4034589B2 (en) * | 2001-06-06 | 2008-01-16 | 株式会社オハラ | Optical glass |
| JP3549198B2 (en) * | 2001-09-21 | 2004-08-04 | Ｈｏｙａ株式会社 | Polarizing glass and manufacturing method thereof |
| US6606885B2 (en) | 2001-10-09 | 2003-08-19 | Corning Incorporated | Infrared, glass polarizer and method |
| US6563639B1 (en) | 2002-01-24 | 2003-05-13 | Corning Incorporated | Polarizing glasses |
| US7104090B2 (en) * | 2002-01-24 | 2006-09-12 | Corning Incorporated | Method of making polarizing glasses |
| US7110179B2 (en) * | 2002-12-19 | 2006-09-19 | Corning Incorporated | Polarizers and isolators and methods of manufacture |
| US20060196228A1 (en) * | 2003-07-31 | 2006-09-07 | Arisawa Mfg. Co., Ltd. | Method for producing polarizing glass |
| JP3696607B2 (en) * | 2003-07-31 | 2005-09-21 | 株式会社有沢製作所 | Manufacturing method of polarizing glass |
| AU2006203042B2 (en) * | 2005-07-20 | 2011-12-15 | Werner Co Australia Pty Ltd | Improved latching means for a combination step and extension ladder |
| CN101215083B (en) * | 2007-01-06 | 2011-07-20 | 湖北新华光信息材料有限公司 | Optical glass for precision profiling |
| US8179595B2 (en) | 2008-01-29 | 2012-05-15 | Corning Incorporated | Polarizing photorefractive glass |
| US20090190214A1 (en) * | 2008-01-29 | 2009-07-30 | Nicholas Francis Borrelli | Polarizing photorefractive glass |
| CN106986537A (en) * | 2017-03-31 | 2017-07-28 | 海盐大民节能玻璃制品有限公司 | A kind of production technology for the glass door of elevator that changes colour |
| CN109704563B (en) * | 2019-03-07 | 2021-09-21 | 湖北戈碧迦光电科技股份有限公司 | Environment-friendly lanthanide optical glass and preparation method and application thereof |
| JP7409636B2 (en) * | 2019-11-27 | 2024-01-09 | 株式会社住田光学ガラス | Multi-component oxide glass, optical element, optical fiber, and method for producing multi-component oxide glass |
| CN114213024B (en) * | 2022-01-19 | 2022-09-30 | 中国耀华玻璃集团有限公司 | Method and device for preparing photoinduced dimming glass by using float double-alloy tank |
| CN116675430A (en) * | 2023-05-23 | 2023-09-01 | 昆明理工大学 | Glass with X-ray color-changing effect and preparation and application methods thereof |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1303171B (en) * | 1966-05-03 | 1971-11-25 | Ernst Leitz Gmbh | |
| US3630765A (en) * | 1969-02-24 | 1971-12-28 | Corning Glass Works | Photochromic glass containing tantalum oxide for optical fiber fabrication |
| US3703388A (en) * | 1970-08-19 | 1972-11-21 | Corning Glass Works | High refractive index photochromic glasses |
| JPS5233642B2 (en) * | 1973-04-02 | 1977-08-30 | ||
| US3999996A (en) * | 1972-05-15 | 1976-12-28 | Jenaer Glaswerk Schott & Gen. | Compatible near-portion phototropic glass |
| US4149896A (en) * | 1972-05-15 | 1979-04-17 | Jenaer Glaswerk Schott & Gen | Phototropic glass for multifocal spectacle-glasses |
| US4284686A (en) * | 1980-06-09 | 1981-08-18 | Corning Glass Works | Spectacle lenses to reduce discomfort from aphakia and certain eye diseases |
| DE3117000C2 (en) * | 1981-04-29 | 1986-05-28 | Schott Glaswerke, 6500 Mainz | Phototropic glass with a refractive index? 1.59, an Abbe number? 40 and a density ≦ 3.2 g / cm? 3? |
| DE3206958C2 (en) * | 1982-02-26 | 1986-09-18 | Schott Glaswerke, 6500 Mainz | Phototropic glass with a refractive index? 1.59, an Abbe number? 44 and a density ≦ 3.0 g / cm? 3? |
| US4390635A (en) * | 1982-03-01 | 1983-06-28 | Corning Glass Works | Alkali metal aluminoborosilicate photochromic glasses |
| US4550087A (en) * | 1984-09-13 | 1985-10-29 | Corning Glass Works | Photochromic comfort glasses |
-
1988
- 1988-07-29 FR FR8810269A patent/FR2634752B1/en not_active Expired - Fee Related
- 1988-12-09 US US07/281,637 patent/US4891336A/en not_active Expired - Lifetime
-
1989
- 1989-01-06 CN CN89100131A patent/CN1023392C/en not_active Expired - Fee Related
- 1989-01-26 KR KR1019890000845A patent/KR960015145B1/en active IP Right Grant
- 1989-03-10 CA CA000593311A patent/CA1333760C/en not_active Expired - Fee Related
- 1989-03-20 EP EP89302737A patent/EP0353834B1/en not_active Expired - Lifetime
- 1989-03-20 ES ES89302737T patent/ES2051999T3/en not_active Expired - Lifetime
- 1989-03-20 DE DE68915222T patent/DE68915222T2/en not_active Expired - Fee Related
- 1989-03-28 IN IN243/MAS/89A patent/IN172239B/en unknown
- 1989-04-21 JP JP1103267A patent/JPH0248426A/en active Pending
- 1989-07-24 AR AR89314487A patent/AR243486A1/en active
- 1989-07-27 BR BR898903740A patent/BR8903740A/en not_active IP Right Cessation
-
1994
- 1994-12-30 HK HK148094A patent/HK148094A/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| US4891336A (en) | 1990-01-02 |
| FR2634752A1 (en) | 1990-02-02 |
| EP0353834A1 (en) | 1990-02-07 |
| JPH0248426A (en) | 1990-02-19 |
| KR900001610A (en) | 1990-02-27 |
| DE68915222D1 (en) | 1994-06-16 |
| IN172239B (en) | 1993-05-15 |
| ES2051999T3 (en) | 1994-07-01 |
| CN1039786A (en) | 1990-02-21 |
| DE68915222T2 (en) | 1994-12-15 |
| AR243486A1 (en) | 1993-08-31 |
| HK148094A (en) | 1995-01-06 |
| KR960015145B1 (en) | 1996-11-01 |
| FR2634752B1 (en) | 1992-09-18 |
| BR8903740A (en) | 1990-03-20 |
| EP0353834B1 (en) | 1994-05-11 |
| CN1023392C (en) | 1994-01-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CA1333760C (en) | High index photochromic glasses | |
| US4549894A (en) | Ultraviolet absorbing photochromic glass of low silver content | |
| US5023209A (en) | Fast fading, high refractive index photochromic glass | |
| US4980318A (en) | High refractive index photochromic glasses | |
| EP0041789A1 (en) | Photochromic glass for spectacle lenses and production thereof | |
| US4742028A (en) | Optical and ophthalmic glasses | |
| EP0855993A1 (en) | High-index glasses that absorb uv radiation | |
| CA1190426A (en) | Very fast fading photochromic glass | |
| US5268335A (en) | Fast strengthening glass lenses | |
| US5426077A (en) | High index brown photochromic glasses | |
| KR900005007B1 (en) | Fast fading photochromic glass | |
| US5424255A (en) | High-refractive index phototropic glass | |
| US4166745A (en) | Refractive index-corrected copper-cadmium halide photochromic glasses | |
| US3998647A (en) | Reversible light-sensitive glass | |
| EP1015394A1 (en) | Improved photochromic glasses | |
| US5422755A (en) | Ultraviolet absorbing, fixed tint lenses | |
| US4757034A (en) | Lightly tinted glasses of variable transmission | |
| EP0252723A1 (en) | Lightly tinted glasses of variable transmission | |
| CA1320505C (en) | Medium refractive index glass suitable for ophthalmic applications | |
| EP0891308B1 (en) | Glasses with a high refractive index and their use as segments of multifocal corrective lenses | |
| GB2121027A (en) | New phototropic glass with brown tint in the light exposed condition | |
| KR800000326B1 (en) | Photochromic glasses | |
| GB2164932A (en) | Glass composition |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKLA | Lapsed |